As part of the 2025 Canadian federal election on April 28, 2025, an election took place for the federal electoral district of Terrebonne, Quebec. This election was a close contest between the incumbent Bloc Québécois candidate, Nathalie Sinclair-Desgagné, and the Liberal candidate Tatiana Auguste.
On the initial count, Liberal candidate Auguste had a 35-vote lead. After the Elections Canada validated the vote, Bloc Québécois Sinclair-Desgagné was declared the winner by 44 votes. A subsequent judicial recount declared Liberal candidate Auguste the winner by 1 vote.
On February 13, 2026, the Supreme Court of Canada annulled the result of the election in the riding, requiring a by-election be held.
In a preliminary count, Auguste was originally assumed to be the winner by 35 votes, but on May 1, the validation of election night results declared Sinclair-Desgagné as the winner by 44 votes. The narrowness of this margin triggered an automatic judicial recount overseen by the Superior Court of Quebec. On May 10, the recount added 74 votes, with 56 of them going to Auguste and 11 to Sinclair-Desgagné. After this recount, the result was reversed, with Auguste certified as the victor by one vote. The shift moved the Liberal seat count to 169, three short of a majority government.
The results became controversial after a would-be Bloc voter disclosed on May 13 that her mail-in ballot was rejected and returned to her due to a postal code misprint on the envelope provided by Elections Canada. On May 14, Elections Canada acknowledged the error but stated that it did not have legal standing to overturn the judicial recount. The following day, the Bloc announced that it would challenge the result in the Superior Court and seek a by-election. The same day, Elections Canada stated that five other mail ballots with the incorrect returning address printed had been rejected for having arrived at the Elections Canada office after the deadline; the statement said that they could not determine if the incorrect address had led to the fatal delay. The application was filed in court on May 23, with the hearing taking place in October.
In September, Elections Canada reported that 115 special ballots had been issued to electors in Terrebonne. Their disposition was as follows:
The case began on October 20 at the courthouse in Saint-Jérôme, and was originally estimated to last three days. No witnesses were scheduled to appear, as all parties were interviewed over the summer and filed consequential affidavits in order to speed up the hearing.
On the first day, it was revealed that the Elections Canada employee estimated that 40 to 60 envelopes had been sent out with the wrong postal code on the return address. He did not think it necessary to inform the returning officer about that, as he had seen envelopes being delivered by Canada Post despite the error, and also noted that the return rate for special ballots was in line with previous elections. The Bloc's advocate, Stéphane Chatigny, submitted that this was still a grave error, which was sufficient to meet the high bar set by the Supreme Court of Canada in a previous contested election case in 2012.
The Liberals' advocate presented his case on the second day, submitting that what happened could be described as an everyday error, and a single vote represented just a margin of 0.0016%. The advocate for Elections Canada stated that it recognized that an error had been committed in the election, but noted that the Supreme Court, while giving high priority to the right to vote, also said that Canadian elections were not designed to attain perfection.
The proceedings achieved notoriety not only in Canada, but also internationally, being reported in such outlets as CNN and The Guardian.
On October 27, the court ruled that a by-election would not be held. Dufour J held that what happened did not constitute an irregularity as defined in Canadian election law, saying, "It is a simple human error, which sometimes occurs in general elections, committed inadvertently and without any dishonest or malicious intent."
On November 3, Sinclair-Desgagné announced that she would be appealing the ruling to the Supreme Court of Canada, saying, "The judgment of the Superior Court of Quebec contains several errors of fact as well as an interpretation of the law and jurisprudence that invites an appeal", and she was also planning to set up a crowdfunding campaign to raise money for the litigation costs.
The Liberal Party subsequently filed a complaint with the Commissioner of Canada Elections, alleging that litigation costs form part of campaign expenses under the Canada Elections Act, and the anonymity given to crowdfunding donors violates the Act's limits on individual and corporate donations. Sinclair-Desgagné responded that she had received two legal opinions on the matter before proceeding with the initiative, and stated that the Liberal claim was "unfounded and malevolent". The federal commissioner then confirmed the legality of Sinclair-Desgagné's actions.
On December 12, the Supreme Court announced that it would be hearing the appeal on February 13, 2026. On that date, the appeal was allowed, and the result of the election in the riding was annulled. Auguste ceased to be an MP immediately. Reasons for the decision will be released at a later date. Elections Canada confirmed the announcement, and the Speaker of the House of Commons gave official notice of the vacancy on February 16.
This is the first time since 1942 that the Supreme Court, on appeal, annulled a federal election, when the 1940 election of Liberal MP Robert Davidson in Stanstead was overturned because of corrupt practices arising from the buying of votes with whiskey and money. That ruling was also the first time the Supreme Court had set aside a lower court decision with respect to an election verdict. This did not automatically trigger the issue of a writ for election: Under the Dominion Controverted Elections Act then in force, the matter had to be referred to the House Privileges and Elections Committee for a recommendation as to how to proceed. The committee would not report until May 1943, clearing the way for the byelection to be held.
Davidson attempted to return to office in the byelection held August 9, 1943, but was defeated by the Bloc Populaire candidate Joseph-Armand Choquette.
Terrebonne's by-election was subsequently called for April 13, 2026, in conjunction with others to be held in Scarborough Southwest and UniversityâÂÂRosedale.
After reviewing its internal procedures, Elections Canada announced that, to avert the possibility of misdirected ballots in future, special ballots will no longer be manually prepared by a riding office, but will be centrally and automatically prepared at its Ottawa office.